Inactivation of galactosyltransferase by lactoperoxidase and N-acetylimidazole.
Galactosyltransferase (UDPgalactose:D-glucose 4-beta-D-galactosyltransferase, EC 2.4.1.22) was totally inactivated by iodination with lactoperoxidase (donor:hydrogen-peroxide oxidoreductase, EC 1.11.1.7). Substrates protected against inactivation. The presence of 10 mM Mn2+ and 1 mM UDPgalactose gave partial protection which was enhanced by the addition of 10 mM N-acetylglucosamine, but not by glucose. These results are consistent with a conformational change upon binding of UDPgalactose. Only monoiodotyrosine and diiodotyrosine were identified in the pronase digest of iodinated galactosyltransferase. Galactosyltransferase was also inactivated with N-acetylimidazole and partial activity was restored by treating acetylated galactosyltransferase with hydroxylamine. These results suggest that tyrosine(s) is essential for galactosyltransferase activity.
D000117:Acetylglucosamine / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D005700:Galactosyltransferases / Q000037:antagonists & inhibitors*; D007093:Imidazoles / Q000494:pharmacology*; D066298:In Vitro Techniques; D007784:Lactoperoxidase / Q000494:pharmacology*; D008345:Manganese / Q000494:pharmacology; D010544:Peroxidases / Q000494:pharmacology*; D014443:Tyrosine; D014531:Uridine Diphosphate Galactose / Q000494:pharmacology
D007093:Imidazoles; D014531:Uridine Diphosphate Galactose; D014443:Tyrosine; D008345:Manganese; D007784:Lactoperoxidase; D010544:Peroxidases; D005700:Galactosyltransferases; D000117:Acetylglucosamine; C012160:N-acetylimidazole